(1) Field of the Invention
The present invention relates to means of forming one or more scannable or fixed direction constant beamwidth beams via a twisted wave front in the near field of an antenna or a single directive scannable beam for radiation or reception of plane or spherical waves which are nearly plane in the far field of the antenna. The beams or beam are substantially frequency independent and have substantially constant beamwidths independent of the frequency used. The beams or beam are formed using an electromagnetic lens and one or more point sources or receivers. They are for electromagnetic applications where multi-channel or very wide band capability is needed in combination with high gain and narrow constant beam width directionality.
(2) Description of the Prior Art
Previous systems for achieving the same results include a first system using various phased array or spherical array processing and beam forming methods. A second system described by Sternberg et al. in U.S. Pat. No. 4,591,864 had cylindrical lenses with line source receiving or radiating elements set at a slight angle to the reference axis or generators of the cylindrical lens surfaces. The invention was described for acoustic systems but also stated its use in the electromagnetic area.
The first system requires extensive data processing and/or electronics to control and scan the beams formed. The second system requires use of line sources or line receiver elements and cannot be done with point sources or point receivers.